Low Temperature Impact Tests in Austempered Ductile Iron and Other Spheroidal Graphite Cast Iron Structures.

Abstract

Impact tests at low temperatures were carried out, aimed at comparing the response of five spheroidal graphite (SG) cast iron with different microstructures and to analyze the influence of the solidification structure size. "Y" blocks with two different thicknesses (13 and 75 mm) were cast using the same industrial melt. The following matrix microstructures were obtained by applying different heat treatments: pearliticferritic (as-cast condition), fully ferritic (sub-critical annealing), fully pearlitic (normalizing) and two ausferritic matrices (ADI grades 2 and 4). Charpy impact tests were performed on unnotched specimens at temperatures ranging from Ϫ100°C to ϩ200°C. The results showed a little variation of the upper and lower shelf energy values with the solidification structure size for each matrix type. However, there was a strong displacement in the transition temperature towards increasing temperatures as the solidification structure size enlarged. This effect is also related to the matrix microstructure. The highest impact energy values were obtained on ADI grade 2 samples, and the lowest ones on the samples with pearlitic matrix.

Effect of Cooling Rate on Microstructure and Mechanical Properties of Thin-Walled Ductile Iron Castings

“…The main factors that influence the structure of ductile iron are chemical composition, cooling rate, liquid treatment, and heat treatment (Ref [1][2][3][4]. The cooling rate of a casting is primarily a function of its section size, pouring temperature, and the material mold ability to absorb the heat.…”

Evaluation of the physical properties of spot welding using ultrasonic testing

“…Figure 10 shows that the microstructures of basic metal are ferrite, and Fig. 11 shows that the microstructure of the heat-affected zone is a mixture of ferrite and tempered pearlite, while the microstructure of According to several studies, pearlite is harder than ferrite, when pearlite appears in the molten zone, it changes the mechanical characteristics (tension-shear, elasticmoduli (E) and longitudinal modulus (C L )) of welding [26,27], and mechanical properties depend on the percentage of pearlite and ferrite content in the microstructure of welding [9], and increasing the percentage of p e a r l i t e l e a d s t o i n c r e a s i n g t h e h a r d n e s s o f microstructures.…”

Transition temperature and fracture mode of as‐castand austempered ductile iron

“…After the specimens have reached the required temperature, they were quickly fractured within a 5 s time interval. According to standard EN 10045, the 5 s time interval is acceptable for the duration of the test, and no significant temperature loss can be expected (Ratto et al , 2001).…”

“…In view of that, it is of great importance to know the behaviour of DI and ADI at low temperatures (Riabov et al , 2002; Batra et al , 2007). One very important criterion for materials selection, especially in low‐temperature applications, is the ductile to brittle transition temperature (Ratto et al , 2001; Fierro et al , 2002).…”